JP7114345B2 - image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus such as a laser printer, copier, and facsimile machine.

Conventionally, in electrophotographic color image forming apparatuses, an intermediate transfer system is used in which toner images are sequentially transferred from each color image forming unit to an intermediate transfer member, and then the toner images are transferred collectively from the intermediate transfer member to a transfer material. is known.

In such an image forming apparatus, each color image forming section has a drum-shaped photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier. As the intermediate transfer member, an intermediate transfer belt formed of an endless belt is widely used. The toner image formed on the photosensitive drum of each image forming unit is transferred to the intermediate transfer belt by applying a voltage from the primary transfer power supply to the primary transfer member provided facing the photosensitive drum through the intermediate transfer belt. be transcribed. The toner image of each color that has been primarily transferred from the image forming section of each color to the intermediate transfer belt is transferred from the intermediate transfer belt to paper or an OHP sheet by applying a voltage from the secondary transfer power supply to the secondary transfer member in the secondary transfer section. are collectively secondary-transferred onto a transfer material such as The toner images of each color transferred onto the transfer material are then fixed onto the transfer material by fixing means.

In an intermediate transfer type image forming apparatus, toner (transfer residual toner) remains on the intermediate transfer belt after the toner image is secondarily transferred from the intermediate transfer belt to the transfer material. Therefore, it is necessary to remove the transfer residual toner remaining on the intermediate transfer belt before the toner image corresponding to the next image is primarily transferred to the intermediate transfer belt.

As a cleaning method for removing transfer residual toner, a blade cleaning method is widely used. In the blade cleaning method, a cleaning blade, which is disposed downstream of the secondary transfer portion with respect to the movement direction of the intermediate transfer belt and serves as a contact member that contacts the intermediate transfer belt, scrapes off the transfer residual toner and collects it in a cleaning container. .

In such a blade cleaning method, the cleaning blade is often arranged so as to always contact the intermediate transfer belt. In this case, if the image forming apparatus is used for a long period of time, foreign matter such as paper dust may be caught in the contact portion (blade nip portion) between the cleaning blade and the intermediate transfer belt, resulting in defective cleaning. Japanese Patent Application Laid-Open No. 2004-200000 discloses a configuration in which an intermediate transfer belt is moved in a direction opposite to that during image formation during non-image formation in order to remove foreign matter caught in a blade nip portion.

JP 2017-122852 A

In the configuration disclosed in Japanese Patent Laid-Open No. 2003-100000, although it is possible to suppress the occurrence of defective cleaning by removing foreign matter caught in the blade nip portion, it is necessary to provide a drive mechanism for rotating the intermediate transfer belt in the reverse direction. cost increase. In addition, when the rotation direction of the intermediate transfer belt is switched to the direction opposite to that during image formation in order to remove foreign matter, it is necessary to interrupt image formation. There was a possibility that this would lead to a drop in throughput.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to suppress the occurrence of defective cleaning without increasing the cost of an image forming apparatus or decreasing the throughput.

The present invention provides an image carrier that carries a toner image, a movable intermediate transfer member that contacts the image carrier and onto which the toner image carried on the image carrier is primarily transferred, and the intermediate transfer member. A contact member that is provided downstream of a secondary transfer portion that secondarily transfers the toner image that has been primarily transferred onto the intermediate transfer member from the intermediate transfer member onto a transfer material, and that contacts the intermediate transfer member in the moving direction. and wherein toner remaining on the intermediate transfer member after passing through the secondary transfer portion is recovered by the contact member to recovery means, wherein the intermediate transfer member comprises the intermediate transfer member and the A region in which the intermediate transfer member and the entire area of the contact member in the width direction of the intermediate transfer member that intersects the moving direction contact the outer peripheral surface side of the contact member, the area being in contact with the intermediate transfer member in the moving direction. A first region having a first coefficient of dynamic friction and a region in which the intermediate transfer member contacts the entire region of the contact member in the width direction, the region being greater than the first coefficient of dynamic friction in the movement direction. and a second region having a second coefficient of dynamic friction equal to the second region, wherein the intermediate transfer member has a plurality of grooves formed in the first region along the moving direction with respect to the width direction. , with respect to the movement direction, the distance of the second area is shorter than the distance of the first area and longer than the contact distance between the contact member and the intermediate transfer body. do.

According to the present invention, it is possible to suppress the occurrence of defective cleaning without increasing the cost of the image forming apparatus or decreasing the throughput.

Schematic cross-sectional view of the image forming apparatus of Example 1 Schematic diagram for explaining the belt cleaning means of the first embodiment. Schematic diagram for explaining the overall configuration of the intermediate transfer belt of the first embodiment. FIG. 4 is a schematic diagram for explaining the surface configuration of the first region of the intermediate transfer belt of Example 1; Schematic diagram for explaining the removal of foreign matter from the intermediate transfer belt of the first embodiment. 7 is a graph showing measurement results of the dynamic friction coefficient at the boundary between the first region and the second region of the intermediate transfer belt of Example 1;

Embodiments of the present invention are illustrated below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangement of the components described in this embodiment should be appropriately changed according to the configuration of the device to which the invention is applied and various conditions, and is within the scope of this invention. is not intended to be limited to the following embodiments.

(Example 1)
[Image forming apparatus]
FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a so-called tandem image forming apparatus having a plurality of image forming units a to d. The first image forming unit a is yellow (Y), the second image forming unit b is magenta (M), the third image forming unit c is cyan (C), and the fourth image forming unit d is black (Bk ) are used to form an image. These four image forming units are arranged in a row at regular intervals, and most of the configurations of the image forming units are substantially common except for the color of the toner to be accommodated. Therefore, the image forming apparatus 100 of this embodiment will be described below using the first image forming unit a.

The first image forming section a has a photosensitive drum 1a that is a drum-shaped photosensitive member, a charging roller 2a that is a charging member, developing means 4a, and drum cleaning means 5a.

The photosensitive drum 1a is an image carrier that carries a toner image, and is rotationally driven in the direction of the arrow R1 in the drawing at a predetermined process speed (200 mm/sec in this embodiment). The developing means 4a includes a developing container 41a containing yellow toner, a developing roller 42a as a developing member for carrying the yellow toner contained in the developing container 41a and developing a yellow toner image on the photosensitive drum 1a, have The drum cleaning unit 5a is a unit for collecting toner adhering to the photosensitive drum 1a. The drum cleaning unit 5a has a cleaning blade that contacts the photosensitive drum 1a, and a waste toner box that stores toner removed from the photosensitive drum 1a by the cleaning blade.

When the image forming operation is started by the control means (not shown) receiving an image signal, the photosensitive drum 1a is rotationally driven. The photosensitive drum 1a is uniformly charged to a predetermined potential (charged potential) with a predetermined polarity (negative polarity in this embodiment) by the charging roller 2a in the course of rotation, and exposed according to the image signal by the exposure means 3a. receive. As a result, an electrostatic latent image corresponding to the yellow component image of the desired color image is formed. Next, the electrostatic latent image is developed by the developing means 4a at the development position and visualized as a yellow toner image (hereinafter simply referred to as toner image). Here, the normal charge polarity of the toner accommodated in the developing means 4a is negative. In this embodiment, the electrostatic latent image is reversely developed with the toner charged to the same polarity as the charging polarity of the photosensitive drum by the charging member. The present invention can also be applied to an image forming apparatus that positively develops an electrostatic latent image.

An intermediate transfer belt 10 as an endless and movable intermediate transfer member is arranged at a position in contact with each of the photosensitive drums 1a to 1d of each of the image forming portions a to d. It is stretched by three shafts of a roller 12 and an opposing roller 13 . The intermediate transfer belt 10 is stretched by a tension roller 12 with a total tension of 60 N, and is moved in the illustrated arrow R2 direction by the rotation of the opposing roller 13 that rotates under the driving force. Although the details will be described later, the intermediate transfer belt 10 in this embodiment is composed of a plurality of layers.

While the toner image formed on the photosensitive drum 1a passes through the primary transfer portion N1a where the photosensitive drum 1a and the intermediate transfer belt 10 are in contact with each other, a positive voltage is applied from the primary transfer power source 23 to the primary transfer roller 6a. Thus, it is primarily transferred to the intermediate transfer belt 10 . After that, the toner remaining on the photosensitive drum 1a without being primarily transferred to the intermediate transfer belt 10 is removed from the surface of the photosensitive drum 1a by being collected by the drum cleaning means 5a.

Here, the primary transfer roller 6 a is a primary transfer member (contact member) provided at a position corresponding to the photosensitive drum 1 a via the intermediate transfer belt 10 and in contact with the inner circumferential surface of the intermediate transfer belt 10 . The primary transfer power source 23 is a power source capable of applying a positive or negative voltage to the primary transfer rollers 6a to 6d. In this embodiment, a configuration in which a voltage is applied from a common primary transfer power source 23 to a plurality of primary transfer members will be described. The present invention can also be applied to a configuration in which they are provided.

Subsequently, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are formed in the same manner, and transferred onto the intermediate transfer belt 10 in order. As a result, a four-color toner image corresponding to the desired color image is formed on the intermediate transfer belt 10 . After that, the four-color toner image carried on the intermediate transfer belt 10 is fed by the paper feeding means 50 in the process of passing through the secondary transfer portion formed by the contact between the secondary transfer roller 20 and the intermediate transfer belt 10 . Secondary transfer is collectively performed on the surface of a transfer material P such as paper or an OHP sheet.

The secondary transfer roller 20 is a nickel-plated steel bar with an outer diameter of 8 mm, covered with a foamed sponge body composed mainly of NBR adjusted to have a volume resistivity of 10 ⁸ Ω·cm and a thickness of 5 mm, and epichlorohydrin rubber, with an outer diameter of 18 mm. are used. The rubber hardness of the foamed sponge body was measured using an Asker hardness tester C type, and the hardness was 30° under a load of 500 g. The secondary transfer roller 20 is in contact with the outer peripheral surface of the intermediate transfer belt 10 and applies a pressing force of 50 N to the opposing roller 13 arranged at a position facing the secondary transfer roller 20 via the intermediate transfer belt 10 . to form a secondary transfer portion N2.

The secondary transfer roller 20 is driven to rotate with respect to the intermediate transfer belt 10 , and current flows from the secondary transfer roller 20 to the counter roller 13 by applying a voltage from the secondary transfer power source 21 . As a result, the toner image carried on the intermediate transfer belt 10 is secondarily transferred onto the transfer material P at the secondary transfer portion. When the toner image on the intermediate transfer belt 10 is secondarily transferred onto the transfer material P, the current flowing from the secondary transfer roller 20 to the opposing roller 13 via the intermediate transfer belt 10 is constant. The voltage applied from the secondary transfer power supply 21 to the secondary transfer roller 20 is controlled. Further, the magnitude of the current for performing the secondary transfer is determined in advance according to the ambient environment where the image forming apparatus 100 is installed and the type of the transfer material P. As shown in FIG. A secondary transfer power supply 21 is connected to the secondary transfer roller 20 and applies a transfer voltage to the secondary transfer roller 20 . Further, the secondary transfer power source 21 is capable of outputting in a range of 100 [V] to 4000 [V].

The transfer material P onto which the four-color toner image has been transferred by secondary transfer is then heated and pressurized by the fixing means 30 so that the four-color toners are melted and mixed and fixed onto the transfer material P. FIG. Toner remaining on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by belt cleaning means 16 (recovery means) provided downstream of the secondary transfer portion N2 with respect to the moving direction of the intermediate transfer belt 10 . The belt cleaning means 16 includes a cleaning blade 16a as a contact member that contacts the outer peripheral surface of the intermediate transfer belt 10 at a position facing the opposing roller 13, and a waste toner container 16b that stores toner collected by the cleaning blade 16a. , have In the following description, the cleaning blade 16a is simply referred to as blade 16a.

In the image forming apparatus 100 of this embodiment, a full-color print image is formed by the above operation.

[Belt cleaning means 16]
FIG. 2(a) is a schematic diagram illustrating the contact state between the blade 16a and the intermediate transfer belt 10, and FIG. 2(b) is an enlarged schematic diagram of the contact point between the blade 16a and the intermediate transfer belt 10. FIG. . The blade 16a in this embodiment is a plate-like member that is long in the width direction of the intermediate transfer belt 10 (hereinafter referred to as the belt width direction) that intersects the moving direction of the intermediate transfer belt 10 (hereinafter referred to as the belt conveying direction). .

The blade 16a in this embodiment has an elastic portion 53 that contacts the intermediate transfer belt 10 and scrapes toner, and a sheet metal portion 52 that supports the elastic portion 53. The elastic portion 53 is a blade member made of polyurethane. is. The blade 16a has a blade shape in which the elastic portion 53 that contacts the intermediate transfer belt 10 has a width of 230 mm and a length of 230 mm. The elastic portion 53 of the blade 16a has a longitudinal width of 230 mm in the belt width direction, a thickness of 2 mm, and a free length from the bonding point with the sheet metal portion 52 of 13 mm. The hardness of the blade 16a is 77 degrees according to the JIS K 6253 standard.

An opposing roller 13 is arranged on the inner peripheral side of the intermediate transfer belt 10 so as to face the blade 16a. The blade 16a is in contact with the surface of the intermediate transfer belt 10 in the counter direction with respect to the belt conveying direction at a position opposed to the opposing roller 13 . That is, the blade 16a is in contact with the surface of the intermediate transfer belt 10 so that the free end in the width direction of the blade 16a faces the upstream side in the belt conveying direction. As a result, a blade nip portion Nb is formed between the blade 16a and the intermediate transfer belt 10, as shown in FIG. 2(b). The blade 16a scrapes toner off the surface of the moving intermediate transfer belt 10 at the blade nip portion Nb and collects it in the waste toner container 16b. In this embodiment, the distance (width) in the belt conveying direction of the blade nip Nb where the blade 16a and the intermediate transfer belt 10 are in contact is 75 μm.

In this embodiment, the blade 16a is arranged with respect to the intermediate transfer belt 10 such that the set angle θ is 22°, the penetration amount δ is 1.5 mm, and the contact pressure is 14N. Here, the set angle .theta. one surface that is substantially orthogonal). The penetration amount δ is the length of the blade 16a overlapping the facing roller 13 in the thickness direction. The contact pressure is defined by the pressing force (linear pressure in the longitudinal direction) from the blade 16a at the blade nip portion Nb, and is measured using a film-type pressure measuring system (trade name: PINCH, manufactured by Nitta). be.

As shown in FIG. 2B, according to the configuration of this embodiment, since the blade 16a is arranged in the counter direction, the tip of the blade 16a in contact with the intermediate transfer belt 10 is frictional with respect to the belt conveying direction. receive power. The frictional force that the tip of the blade 16a receives is a force that bends the tip of the blade 16a following the belt conveying direction. As a result, the contact portion of the blade 16a is curved as shown in FIG. A region in which the blade 16a is caught at this time is defined as a caught portion M, and a distance (length) of the caught portion M in the belt conveying direction is defined as a caught amount m.

It should be noted that the blade 16a dams up the toner remaining on the intermediate transfer belt 10 by applying pressure to the intermediate transfer belt 10 at the winding portion M of the blade 16a that is wound by the frictional force between the intermediate transfer belt 10 and the intermediate transfer belt 10. . After that, the toner dammed up by the blade 16a is collected in the waste toner container 16b. Therefore, in order to ensure toner collectability, the blade 16a is brought into contact with the intermediate transfer belt 10 with a predetermined pressure applied so that the toner does not slip through.

However, if the pressure of the blade 16a against the intermediate transfer belt 10 becomes too high, the frictional force applied to the tip of the blade 16a increases, and the winding amount m of the winding portion M of the blade 16a also increases. If the entrainment amount m becomes too large, a phenomenon in which the blade 16a, which is in contact with the intermediate transfer belt 10 in the counter direction, comes into contact along the belt conveying direction (hereafter referred to as "mocking"). may occur. In the event that the blotch occurs, it becomes difficult for the blade 16a to dam up the toner remaining on the intermediate transfer belt 10, which may result in defective cleaning. Therefore, in order to ensure the recoverability of the toner remaining on the intermediate transfer belt 10, it is necessary to appropriately set the winding amount m of the blade 16a.

As means for adjusting the winding amount m of the blade 16a, there is a method of adjusting the dynamic friction coefficient of the intermediate transfer belt 10 to adjust the frictional force applied to the winding portion M of the blade 16a. For example, the surface of the intermediate transfer belt 10 is provided with a plurality of grooves and unevenness along the belt conveying direction to reduce the contact area between the blade 16a and the intermediate transfer belt 10, thereby reducing the coefficient of dynamic friction between the intermediate transfer belt 10 and the blade 16a. It is possible to reduce the friction force by Thereby, the winding amount m of the blade 16a with respect to the intermediate transfer belt 10 can be adjusted. In addition, as a means for adjusting the amount of entrainment m of the blade 16a, there is a method of applying a lubricant such as graphite fluoride to the tip of the blade 16a in advance to adjust the frictional force applied to the entrainment portion M of the blade 16a.

[Intermediate transfer belt]
Next, the configuration of the intermediate transfer belt 10 in this embodiment will be described. FIG. 3 is a schematic diagram illustrating the overall configuration of the intermediate transfer belt 10. As shown in FIG. FIG. 4A is a schematic diagram of the intermediate transfer belt 10 when the intermediate transfer belt 10 is cut in a direction substantially orthogonal to the belt conveying direction (seen along the belt conveying direction) in the region X of FIG. 2 is an enlarged partial sectional view; FIG. FIG. 4(b) shows in more detail the surface layer 40 of the intermediate transfer belt 10, which will be described later, in a cross section similar to that of FIG. 3(a).

The intermediate transfer belt 10 is an endless belt member (or film member) composed of two layers, a base layer 41 and a surface layer 40. The intermediate transfer belt 10 has a circumferential length of 700 mm and a longitudinal width of 250 mm in the belt width direction. be. Here, the base layer is defined as the thickest layer among the layers constituting the intermediate transfer belt 10 in the thickness direction of the intermediate transfer belt 10 . In this embodiment, the base layer 41 is a layer having a thickness of 70 μm and made by dispersing a quaternary ammonium salt, which is an ion conductive agent as an electric resistance adjusting agent, in polyethylene naphthalate resin. Also, the surface layer 40 is a layer formed on the outer peripheral surface side of the intermediate transfer belt 10 . In the surface layer 40 of this embodiment, antimony-doped zinc oxide is dispersed as the electric resistance adjusting agent 43 in the acrylic resin as the base material 46, and polytetrafluoroethylene (PTFE), which is fluorine-containing particles, is used as the solid lubricant 44. ) is a 3 μm thick layer doped with particles.

The volume resistivity of the intermediate transfer belt 10 in this embodiment is 1×10 ¹⁰ Ω·cm. The volume resistivity was measured by connecting a UR probe (model MCP-HTP12) to Hiresta-UP (MCP-HT450) manufactured by Mitsubishi Chemical Corporation, applying a voltage of 100 V, and measuring for 10 seconds. The environment of the measurement chamber for measuring the volume resistivity was set at a temperature of 23° C. and a humidity of 50%, and the volume resistivity of the intermediate transfer belt 10 was measured after being left in the measurement chamber for 4 hours.

Further, the materials of the base layer 41 and the surface layer 40 are not limited to those described above, and other materials may be used. For example, as the base layer 41, other than polyethylene naphthalate resin, polycarbonate, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polymethylpentene-1, polystyrene, polyamide, polysulfone, polyarylate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate can be used. , polyphenylene sulfide, polyether sulfone, polyether nitrile, thermoplastic polyimide, polyether ether ketone, thermotropic liquid crystal polymer, and polyamic acid. These can also be mixed and used 2 or more types.

Regarding the surface layer 40, curable resins such as melamine resins, urethane resins, alkyd resins, and fluorine-based curable resins (fluorine-containing curable resins) can be used as organic materials other than acrylic resins. Examples of inorganic materials include alkoxysilane/alkoxyzirconium-based materials and silicate-based materials. Organic/inorganic hybrid materials include inorganic fine particle-dispersed organic polymer materials, inorganic fine particle-dispersed organoalkoxysilane materials, acrylic silicon materials, and organoalkoxysilane materials.

From the viewpoint of strength such as wear resistance and crack resistance of the surface layer 40 of the intermediate transfer belt 10, resin materials (curable resins) are preferable among the curable materials. An acrylic resin obtained by curing a copolymer is preferred. In this embodiment, the surface layer 40 of the intermediate transfer belt 10 is formed by coating the surface of the base layer 41 with a liquid containing an ultraviolet curable monomer and/or oligomer component and irradiating it with energy rays such as ultraviolet rays. It was obtained by curing with

Examples of the electronically conductive material include particulate, fibrous, or flaky carbon-based conductive fillers such as carbon black, PAN-based carbon fiber, and pulverized expanded graphite. Further, for example, particulate, fibrous or flaky metallic conductive fillers such as silver, nickel, copper, zinc, aluminum, stainless steel and iron are included. Further examples include particulate metal oxide-based conductive fillers such as zinc antimonate, antimony-doped tin oxide, antimony-doped zinc oxide, tin-doped indium oxide, and aluminum-doped zinc oxide. Examples of ionically conductive materials include ionic liquids, conductive oligomers and quaternary ammonium salts. One or more of these conductive materials may be appropriately selected, and an electronically conductive material and an ionically conductive material may be mixed and used.

As shown in FIGS. 3 and 4(a) and 4(b), the intermediate transfer belt 10 of this embodiment has a region X (second 1 region) and a region Y (second region) in which the surface layer 40 is not subjected to surface treatment. Areas X and Y are areas formed continuously over the entire contact area between the blade 16a and the intermediate transfer belt 10 in the belt width direction orthogonal to the belt conveying direction.

Further, as shown in FIG. 3, the intermediate transfer belt 10 has a first switching point for switching from the area X to the area Y and a second switching point for switching from the area Y to the area X with respect to the belt conveying direction. have one each. That is, the intermediate transfer belt 10 has one area X formed continuously in the belt conveying direction and one area Y formed continuously in the belt conveying direction. In the following description, the distance from the first switching point to the second switching point is defined as the distance of the area Y, and the distance from the second switching point to the first switching point is defined as the distance of the area X with respect to the belt conveying direction. In this embodiment, the distance of region Y is 5 mm and the distance of region X is 695 mm.

In this embodiment, in the region X, a plurality of grooves (groove shape, groove portion) 45 are formed along the belt conveying direction with respect to the belt width direction. On the other hand, the grooves 45 are not formed in the region Y, and due to this configuration, the dynamic friction coefficient in the region Y of the intermediate transfer belt 10 of this embodiment is larger than the dynamic friction coefficient in the region X. Incidentally, as shown in the schematic diagram of FIG. 3, in the region X, the grooves 45 are continuously formed in the belt conveying direction.

The configuration of the grooves 45 formed in the intermediate transfer belt 10 in the region X will be described below with reference to FIGS. 4(a) and 4(b). Note that the shape of the groove 45 in the following description was measured using L-trace & NanoNavi II (manufactured by SII Nano Technology) in the DFM mode using a high aspect probe SI-40H for the cantilever.

As shown in FIG. 4B, the width W of the opening of the groove 45 (hereinafter simply referred to as width W) in the direction (belt width direction) substantially orthogonal to the longitudinal axis direction is 1 μm. Further, the depth d from the surface (opening) of the surface layer 40 on which the grooves are not formed to the bottom of the grooves 45 in the thickness direction of the intermediate transfer belt 10 (hereinafter simply referred to as the depth d) is 2 μm. . Further, the interval K between the grooves 45 in the direction substantially orthogonal to the belt conveying direction (hereinafter simply referred to as pitch K) is 20 μm.

From the viewpoint of cleaning performance, it is preferable that the width W of the groove 45 is up to about half the average particle size of the toner. If the width W of the groove 45 is too wide, the toner may pass through the blade nip portion Nb when it is caught in the groove 45, resulting in poor cleaning. Further, if the width W of the groove 45 is too narrow, the contact area between the blade 16a and the intermediate transfer belt 10 becomes too large, which increases the friction at the blade nip portion Nb and promotes wear of the tip of the blade 16a. There is a risk of Therefore, in the configuration of this embodiment, it is preferable to set the width W of the groove 45 to 0.5 μm or more and 3 μm or less.

In this embodiment, since the thickness of the surface layer 40 is 3 μm, the grooves 45 do not reach the base layer 41 and exist only in the surface layer 40 . The grooves 45 are formed continuously over the entire circumference of the intermediate transfer belt 10 along the circumferential direction (rotational direction) of the intermediate transfer belt 10 . In this embodiment, the surface of the intermediate transfer belt 10 is formed with grooves by pressing a mold having a convex shape on the surface against the surface layer 40 .

Here, the thickness of the surface layer 40 must be a thickness that allows the grooves 45 to be formed, that is, the depth d of the grooves 45 or more. When the thickness of the surface layer 40 is smaller than the depth d of the grooves 45, the grooves 45 reach the base layer 41, and the substance added to the base layer 41 precipitates on the surface of the surface layer 40, resulting in defective cleaning. There is a risk of On the other hand, if the thickness of the surface layer 40 is too large, the surface layer 40 made of acrylic resin may be cracked, resulting in poor cleaning. Therefore, in the configuration of the present embodiment, the thickness of the surface layer 40 is preferably set between 1 μm and 5 μm, and is set between 1 μm and 3 μm in consideration of cracking of the surface layer 40 during long-term use. is more preferable.

As described above, in this embodiment, by providing the region X in which the groove 45 is formed, the contact area between the blade 16a and the intermediate transfer belt 10 is reduced, and the dynamic friction coefficient of the intermediate transfer belt 10 is adjusted to allow the blade 16a to move. The frictional force applied to the winding part M is adjusted. With this configuration, it is possible to suppress wear of the blade 16a. In this embodiment, the groove 45 is formed in a range wider than the width of the blade 16a in the belt width direction. In other words, the intermediate transfer belt 10 has a configuration in which the widths of the regions X and Y are wider than the width of the blade 16a in the belt width direction. Thereby, it is possible to stably suppress wear of the blade 16a over the entire width of the blade 16a.

<Removal of Foreign Matter in Blade Nip Portion Nb>
As shown in FIG. 3, the intermediate transfer belt 10 of this embodiment has a region X in which the surface layer 40 is formed with the grooves 45 and a region Y in which the surface layer 40 is not formed with the grooves 45 . Some grooves are processed. In the region X, the contact area between the blade 16a and the intermediate transfer belt 10 is reduced by forming the grooves 45, and the surface area of the intermediate transfer belt 10 is increased, so that the exposed area of the solid lubricant 44 is increased. increase. As a result, in the region X, the dynamic friction coefficient between the blade 16a and the intermediate transfer belt 10 is lowered.

Table 1 is a table comparing the dynamic friction coefficient and the entrainment amount m in the region X and the region Y. Note that the coefficient of dynamic friction and the amount of entrainment m corresponding to the area X and the area Y are the intermediate transfer belt on which the grooves 45 are formed over the entire surface in the belt conveying direction (consisting of only the area X) and the belt on which no grooves are formed ( It was obtained by measuring with respect to the intermediate transfer belt (composed only of area Y).

Here, the coefficient of dynamic friction was measured using a surface property tester (“Haydon 14FW” manufactured by Sintokagaku Co., Ltd.) and using a urethane rubber ball indenter (outer diameter 3/8 inch, rubber hardness 90 degrees) as a measuring indenter. The measurement conditions were a test load of 50 gf, a speed of 10 mm/sec, and a measurement distance of 50 mm.The value of the dynamic friction coefficient in Table 1 is the friction force (gf ) divided by the test load (gf).

Further, the magnitude of the winding amount m of the blade 16a was measured as follows. First, a blade 16a having a tip coated with graphite fluoride is installed on the intermediate transfer belt 10, and the image forming apparatus is operated for two minutes in a non-image forming state. , the tip of the blade 16a is observed with a microscope. Then, the width of the portion where the graphite fluoride applied to the tip of the blade 16a was peeled off was measured by rubbing against the intermediate transfer belt 10, and this width was defined as the winding amount m.

As shown in Table 1, when the dynamic friction coefficient changes by 0.05 or more, the entrainment amount m changes by about 3 μm. That is, according to the intermediate transfer belt 10 having the region X having the first dynamic friction coefficient and the region Y having the second dynamic friction coefficient larger than the first dynamic friction coefficient, the blade nip portion Nb The magnitude of the winding amount m of the blade 16a can be changed.

FIG. 5(a) is a schematic enlarged cross-sectional view illustrating a state in which the blade 16a is in contact with the region X at the blade nip portion Nb. FIG. 5B is a schematic enlarged cross-sectional view illustrating a state in which the blade 16a is in contact with the region Y after the blade 16a has passed the first switching point due to the movement of the intermediate transfer belt 10. FIG. FIG. 5C is a schematic enlarged cross-sectional view illustrating a state in which the blade 16a is in contact with the region X again after the blade 16a passes through the second switching point due to the movement of the intermediate transfer belt 10. FIG. .

When the blade 16a is passing through the region X, the shape of the winding portion M of the blade 16a is as shown in FIG. 5(a). Then, as shown in FIG. 5B, when the intermediate transfer belt 10 rotates, the blade 16a comes into contact with the region Y after passing through the first switching point. FIG. 6 shows the results of continuous measurement of the dynamic friction coefficient from region X to region Y. In FIG. As shown in FIG. 6, the dynamic friction coefficient increases at the position where the region X is switched to the region Y (first switching point). Then, as shown in FIG. 5(b), the shape of the entrapment portion M of the blade 16a is deformed, and the entrainment amount m increases. After that, when the blade 16a comes into contact with the region X again, the shape of the winding portion M returns to the initial shape as shown in FIG. 6(c).

As described above, when the blade 16a passes through the first switching point and the second switching point, the shape of the involved portion M of the blade 16a changes, and the size of the involved amount m changes. As a result, the contact state between the blade 16a and the intermediate transfer belt 10 changes, and as a result, as shown in FIGS. removed.

If the foreign matter Q is caught in the blade nip portion Nb and is not removed, the state of contact of the blade 16a with the intermediate transfer belt 10 becomes unstable, and cleaning failure may occur. Therefore, conventionally, a method of switching the moving direction of the intermediate transfer belt 10 is known as a method of removing the foreign matter Q caught in the blade nip portion Nb. However, according to the configuration of the present embodiment, the movement of the intermediate transfer belt 10 can change the winding amount m of the winding portion M of the blade 16a to remove the foreign matter Q. is not required to move in the direction opposite to that during image formation. That is, there is no need to provide a driving mechanism for moving the intermediate transfer belt in the reverse direction, or to interrupt image formation to move the intermediate transfer belt in the reverse direction.

Here, in this embodiment, the distance of the region Y is set larger than the distance of the blade nip portion Nb and shorter than the distance of the region X with respect to the belt conveying direction. With respect to the belt conveying direction, the entire area of the blade nip portion Nb enters the region Y, causing a change in the shape of the entrapment portion M of the blade 16a, and the foreign matter Q can be removed. It must be set larger than the nip portion Nb. On the other hand, if the distance of the region Y in the belt conveying direction is longer than the distance of the region X, the contact time between the region Y having a large coefficient of dynamic friction and the blade 16a becomes longer, and the blade 16a is likely to be worn, resulting in poor cleaning. may become more likely to occur. Therefore, it is necessary to set the distance of the area Y to be shorter than the distance of the area X with respect to the belt conveying direction.

As described above, according to the configuration of the present embodiment, it is possible to suppress the occurrence of defective cleaning without increasing the cost of the image forming apparatus or reducing the throughput.

It should be noted that foreign matter Q can be effectively removed if the amount of change in the amount of entrainment m in the entrained portion M of the blade 16a is approximately the same as that of the foreign matter Q. Since the size of paper dust, which is a typical foreign matter Q, is about several μm, it is desirable to set the amount of change in the entrainment amount m to that extent. Further, it is desirable that the width of the region Y be larger than the width of the blade 16a in the belt width direction. This is because if the width of the region Y is greater than the width of the blade nip portion Nb, the entire blade 16a can be operated when passing through the first switching point, and the winding portion M can be moved significantly.

[Evaluation of cleaning performance]
Next, in the image forming apparatus 100, the intermediate transfer belt 10 of this embodiment and the intermediate transfer belts of Comparative Examples 1 and 2 were evaluated for cleanability. Here, as Comparative Example 1, an intermediate transfer belt having no grooves or the like formed on the surface and having a uniform coefficient of dynamic friction over the entire area in the belt conveying direction was used. As Comparative Example 2, an intermediate transfer belt having grooves formed on its surface and having a uniform coefficient of dynamic friction over the entire area in the belt conveying direction was used.

To evaluate cleanability, letter-size paper (trademark Vitality, manufactured by Xerox) was used to form a character image of 1% for each color in a two-sheet intermittent mode. An image was formed to In addition, evaluation was performed in the environment of the temperature of 15 degreeC, and the humidity of 10%.

The following method was used to confirm the occurrence of cleaning failures every 5,000 sheets in the durability evaluation described above. First, after forming a red solid image (a solid image of 100% yellow and 100% magenta) with the output from the secondary transfer power supply 21 turned off (0 V), the output from the secondary transfer power supply 21 is set to an appropriate value. 5 sheets of transfer material P on which no image is formed are continuously fed. That is, by confirming whether the toner of the red solid image remaining on the transfer material P without being transferred at the secondary transfer portion N2 is removed by the blade 16a, it is confirmed whether or not cleaning failure has occurred.

If the toner of the solid red image can be removed from the intermediate transfer belt 10, the five sheets of transfer material P which are continuously fed are substantially completely blank. On the other hand, if the toner of the red solid image cannot be removed, the toner passing through the blade 16a reaches the secondary transfer portion N2 again, and the toner is transferred to the five transfer materials P that are continuously fed, resulting in cleaning failure. Output as an image. The occurrence of the cleaning failure as described above was confirmed every time 5,000 sheets of the transfer material P were fed, and 100,000 sheets of the transfer material P were evaluated.

As a result of evaluating the cleanability, in the configuration of this example, cleaning failure did not occur until 100,000 sheets were passed, but in the configuration of Comparative Example 1, cleaning failure occurred after 20,000 sheets were passed. In the configuration of No. 2, cleaning failure occurred after 50,000 sheets of paper were fed.

When the tip of the cleaning blade used in Comparative Example 1 was observed under a microscope, it was found that the urethane rubber was worn by friction with the intermediate transfer belt 10 and the tip of the cleaning blade was chipped. This is because the large coefficient of dynamic friction between the intermediate transfer belt 10 and the cleaning blade tends to cause abrasion of the cleaning blade at the blade nip portion. When the tip of the cleaning blade used in Comparative Example 2 was observed under a microscope, it was confirmed that paper dust generated from the transfer material P adhered to the tip of the cleaning blade. In the intermediate transfer belt of Comparative Example 2, since the coefficient of dynamic friction was uniform over the entire area in the belt conveying direction, it was considered that the paper dust accumulated in the blade nip portion and the transfer residual toner slipped through. .

As described above, areas having different coefficients of dynamic friction are formed on a part of the intermediate transfer belt 10 to change the contact state of the blade 16a and allow foreign matter caught in the blade nip portion to pass through, thereby preventing cleaning failures. It can suppress the occurrence.

[Other Examples]
Although the groove 45 is not formed in the region Y of the intermediate transfer belt 10 in the first embodiment, the present invention is not limited to this. That is, if the value of the dynamic friction coefficient in the region Y is larger than that in the region X, it is possible to remove the foreign matter Q by changing the winding amount m of the blade 16a as in the first embodiment. Therefore, for example, grooves having a lower density than the grooves formed in the area X may be formed in the area Y of the intermediate transfer belt 10 to have different dynamic friction coefficients.

In Example 1, the surface layer 40 in the region X was processed to form the grooves 45 in order to change the dynamic friction coefficient of the intermediate transfer belt 10, but as another method, a method of changing the polishing strength is also possible. be. Specifically, the region X of the outer peripheral surface of the intermediate transfer belt 10 is polished with a rough wrapping film (Lapika #2000 (trade name), manufactured by KOVAX), and the region Y is polished with a fine wrapping film (Lapika #10000 (trade name). ), manufactured by KOVAX). Polishing with a rough lapping film is greater than polishing with a fine lapping film, and since the surface area of the solid lubricant exposed increases, the coefficient of dynamic friction can be reduced.

Another method for changing the coefficient of dynamic friction between the regions X and Y is to spray coat the region X with a coating liquid containing lubricating particles. The surface roughness of the spray-applied portion is large, and since the exposed area of the solid lubricant increases, the coefficient of dynamic friction can be reduced.

REFERENCE SIGNS LIST 1 image forming apparatus 2 photosensitive drum 8 intermediate transfer belt 16 belt cleaning means 16a cleaning blade

Claims (16)

an image carrier that carries a toner image; a movable intermediate transfer member that contacts the image carrier and onto which the toner image carried on the image carrier is primarily transferred; a contact member that is provided downstream of a secondary transfer unit that secondarily transfers the toner image that has been primarily transferred onto the intermediate transfer member from the intermediate transfer member onto a transfer material, and that contacts the intermediate transfer member. an image forming apparatus in which toner remaining on the intermediate transfer member after passing through the secondary transfer portion is recovered by the contact member to a recovery means;
The intermediate transfer body has an outer circumferential surface where the intermediate transfer body and the contact member are in contact with each other. a first region having a first coefficient of dynamic friction in the moving direction, and a region in which the intermediate transfer member and the entire area of the contact member in the width direction abut, wherein the a second region having a second dynamic friction coefficient larger than the first dynamic friction coefficient in the direction of movement;
the intermediate transfer member has a plurality of grooves formed in the first region along the moving direction with respect to the width direction;
With respect to the movement direction, the distance of the second area is shorter than the distance of the first area and longer than the contact distance between the contact member and the intermediate transfer body. Image forming device. The intermediate transfer member is an endless belt member, and with respect to the moving direction, the intermediate transfer member has a first switching point for switching from the first area to the second area, and the second area. 2. The image forming apparatus according to claim 1, wherein one second switching point for switching from the first area to the first area is formed. Regarding the moving direction, the distance from the first switching point to the second switching point is the distance of the second area, and the distance from the second switching point to the first switching point is the first area. 3. The image forming apparatus according to claim 2, wherein the distance is . 4. The image forming apparatus according to claim 1 , wherein in the first area, the plurality of grooves are formed continuously in the moving direction. 5. The image forming apparatus according to claim 4 , wherein the second area of the intermediate transfer member does not have a plurality of grooves along the moving direction with respect to the width direction. the intermediate transfer member has a plurality of grooves formed in the second region along the moving direction with respect to the width direction;
5. The image forming apparatus according to claim 4, wherein the density of the plurality of grooves in the second region is lower than the density of the plurality of grooves in the first region with respect to the width direction. 7. The image forming apparatus according to claim 1 , wherein a difference between the value of the first coefficient of dynamic friction and the value of the second coefficient of dynamic friction is 0.05 or more. 8. The image forming apparatus according to claim 1 , wherein the surface roughness value in the second area is smaller than the surface roughness value in the first area. 9. The image according to any one of claims 1 to 8 , wherein the width of the first region and the width of the second region are larger than the width of the contact member in the width direction. forming device. The intermediate transfer body includes a base layer, which is the thickest layer among a plurality of layers constituting the intermediate transfer body in the thickness direction of the intermediate transfer body and to which an ion conductive agent is added, and a surface of the base layer. The image according to any one of claims 1 to 9 , wherein the first region and the second region are regions formed on the surface layer. forming device. 11. The image forming apparatus according to claim 10 , wherein the thickness of the surface layer is set to 3 [mu]m or less. 12. The image forming apparatus according to claim 10 , wherein the surface layer is made of acrylic copolymer. 13. The image forming apparatus according to claim 10 , wherein fluorine -containing particles are added to said surface layer. 14. The image forming apparatus according to claim 13 , wherein the fluorine-containing particles are polytetrafluoroethylene (PTFE). 15. The image forming apparatus according to claim 1 , wherein the contact member is a blade made of polyurethane. 16. The image forming apparatus according to claim 1, wherein the contact member contacts the intermediate transfer member in a counter direction.

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